title: E3 ubiquitin ligase Fbw7 negatively regulates granulocytic differentiation by targeting G-CSFR for degradation.
abstract: Tight control between activation and attenuation of granulocyte colony stimulating factor receptor (G-CSFR) signaling is essential to regulate survival, proliferation and differentiation of myeloid progenitor cells. Previous studies demonstrated negative regulation of G-CSFR through endosomal-lysosomal routing and ubiquitin-proteasome mediated degradation. However, very few E3 ubiquitin ligases are known to target G-CSFR for ubiquitin-proteasome pathway. Here we identified F-box and WD repeat domain-containing 7 (Fbw7), a substrate recognizing component of Skp-Cullin-F box (SCF) E3 ubiquitin Ligase physically associates with G-CSFR and promotes its ubiquitin-mediated proteasomal degradation. Our data shows that Fbw7 also interacts with and degrades G-CSFR-T718 (a truncated mutant of G-CSFR found in severe congenital neutropenia/acute myeloid leukemia (SCN/AML patients)) though at a quite slower rate compared to G-CSFR. We further show that glycogen synthase kinase 3 beta (GSK3β), like Fbw7 also targets G-CSFR and G-CSFR-T718 for degradation; however, Fbw7 and GSK3β are interdependent in targeting G-CSFR/G-CSFR-T718 for degradation because they are unable to degrade G-CSFR individually when either of them is knocked down. We further show that Fbw7 mediated downregulation of G-CSFR inhibits signal transducer and activator of transcription 3 (STAT3) phosphorylation which is required for G-CSF dependent granulocytic differentiation. In addition, our data also shows that inhibition of Fbw7 restores G-CSFR signaling leading to enhanced STAT3 activity resulting in massive granulocytic differentiation. These data indicate that Fbw7 together with GSK3β negatively regulates G-CSFR expression and its downstream signaling.
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India.
authors.forename: Savita
authors.initials: S
authors.lastname: Lochab
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India.
authors.forename: Pooja
authors.initials: P
authors.lastname: Pal
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India.
authors.forename: Isha
authors.initials: I
authors.lastname: Kapoor
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India.
authors.forename: Jitendra Kumar
authors.initials: JK
authors.lastname: Kanaujiya
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India.
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Sanyal
authors.affiliation: Division of Hematology and Oncology, University Hospital of Leipzig, Johannissallee 32A, 04103 Leipzig, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Behre
authors.affiliation: Drug Target Discovery and Development Division, CSIR-Central Drug Research Institute (CSIR-CDRI), Sector-10, Jankipuram Extension, Lucknow, 226031 UP, India. Electronic address: arun3vedi@yahoo.com.
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Trivedi
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D044783:F-Box Proteins / Q000378:metabolism*; D000073979:F-Box-WD Repeat-Containing Protein 7; D055785:Gene Knockdown Techniques; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006098:Granulocytes / Q000166:cytology* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D059748:Proteolysis; D016188:Receptors, Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D044783:F-Box Proteins; D000073979:F-Box-WD Repeat-Containing Protein 7; C513273:FBXW7 protein, human; C513272:Fbxw7 protein, mouse; D050505:Mutant Proteins; D016188:Receptors, Granulocyte Colony-Stimulating Factor; D050796:STAT3 Transcription Factor; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3; D046988:Proteasome Endopeptidase Complex
keywords: Fbw7; G-CSFR; GSK3β; Ubiquitin–proteasome degradation